Since plasma display panels (PDPs) allow high speed display and make it easy to make large-sized display compared to liquid crystal panels, they are used in such areas as OA apparatuses and public relations display units. Furthermore, they are highly expected to be applicable in the area of high grade television sets.
With such expansion of application, color PDPs with many fine display cells attract attention. In a PDP, plasma discharge is caused between anodes and cathodes facing each other in discharge spaces formed between a front glass substrate and a rear glass substrate, and the ultraviolet ray generated by a gas contained in the discharge spaces is applied to the phosphors provided in the discharge spaces, for displaying. A simple structural view showing an AC type PDP is shown in FIG. 1. In this case, to keep the spread of discharge in certain regions for displaying in specified cells and to secure uniform discharge spaces, barrier ribs (also called barriers or ribs) are formed. In the case of AC type PDP, the barrier ribs are formed in stripes.
The barrier ribs are about 30 to 80 .mu.m wide and 100 to 200 .mu.m high. Usually the barrier ribs are formed by printing a paste containing a glass powder onto the front glass substrate or rear glass substrate in stripes by screen printing, drying, repeating the printing and drying 10 to 20 times to achieve a predetermined height, and firing. However, screen printing presents a problem in that especially when the panel size is larger, it is difficult to align the discharge electrodes preformed on the front transparent flat plate, with the printing positions of the glass paste, not allowing a high position accuracy to be achieved. In addition, since the glass paste is overlapped 10 to 20 times for printing, the barrier ribs become wavy and disordered at the bottoms and cannot be accurate enough in height, so that the display quality, working efficiency and yield are delivered. Especially in the case of barrier ribs with a width of 50 .mu.m or less formed at a pitch of 100 .mu.m or less, the paste is likely to bleed at the bottoms due to thixotropy, and it is difficult to form sharp barrier ribs free from residue.
Since PDPs larger in area and higher in resolution are being adopted, it becomes technically more and more difficult to produce highly accurate barrier ribs with a high aspect ratio by screen printing, and screen printing becomes less advantageous in view of cost.
As methods to solve these problems, U.S. Pat. Nos. 4,885,963 and 5,209,688 and Japanese Patent Laid-Open (Kokai) Nos. 5-342992 and 6-295676 propose methods for forming barrier ribs by photolithography using a photosensitive paste. However, is these methods present problems, for example, in that dense barrier ribs cannot be obtained after firing because the glass content of the photosensitive paste is small, and in that the photosensitive paste is low in sensitivity and resolution. For these reasons, it was necessary to repeat the photosensitive paste coating, exposure and development, for obtaining barrier ribs with a high aspect ratio. However, the repetition of coating, exposure and development causes the problem of positioning and restricts the cost reduction.
Japanese Patent Laid-Open (Kokai) No. 8-50811 proposes a method of forming barrier ribs by one single exposure time using a photosensitive glass paste. However, this method presents problems, for example, in that when a pattern with thin barrier ribs is formed, the pattern meanders, falls or peels after exposure and development and that when the pattern is fired to form barrier ribs, the barrier ribs are broken or peeled. Furthermore, depending on the sectional form of the barrier ribs, disadvantageously, the phosphors cannot be uniformly applied.